DK149191B - ANTIVIRAL ACTIVE PHARMACEUTICAL OIL-IN-WATER FORMULATION OF 9- (2-HYDROXYETHOXYMETHYL) GUANINE (ACYCLOVIR) - Google Patents

Description

in 149191

The invention relates to an antivirally active pharmaceutical oil-in-water formulation of 9- (2-hydroxyethoxy-methylguanine (acyclovir) or a salt or ester thereof as active ingredient containing a 5 dispersion oil phase and a continuous aqueous phase containing the said active ingredient and a polyhydric alcohol.

Acyclovir and pharmaceutically acceptable salts and esters thereof are known to possess antiviral activity against 10 different classes of DNA and RNA viruses, both in vitro and in vivo, cf. English Patent No. 1,523,865. In particular, the compound is effective against herpes simplex virus causing keratitis herpetica in rabbits, encephalitis herpetica in mice and cutaneous herpes in guinea pigs.

Acyclovir has the disadvantage of having a low solubility in water and is almost completely insoluble in hydrophobic solvent systems. Accordingly, it is difficult to prepare a topical formulation containing a sufficiently dissolved concentration of active ingredient for it to exert its full effect, and likewise it is difficult to optimize the migration of the compound into the skin. In addition to ease of release, it is also important that any formulation of a pharmaceutically active compound is stable for longer periods of time, does not deteriorate in effect, does not discolor or form insoluble substances or complexes, and is not too irritating to the skin or mucosa.

In Example 26 of English Patent No. 1,523,865 30, the ingredients are disclosed in an oil-in-water cream containing 5% w / w acyclovir, among which components are 5% w / w propylene glycol. The function of the propylene glycol in the formulation of Example 26 is to act as a moisture-binding agent, i.e. as a hygroscopic component to enhance the cosmetic feel of the product and also to limit drying during storage. In animal experiments, this formulation and a formulation of aqueous cream B.P. (British Pharma copé) containing acyclovir does not recover very quickly, probably due to an insufficient amount of active ingredient in solution as well as poor penetration of the active ingredient into the skin.

Due to the lipid nature of the skin surface, especially the stratum corneum, it has long been believed that the active ingredient in an emulsion to obtain good penetration of the skin must be present in the oil phase so that it can disperse in the lipid components of the skin.

It has now been found that in order to obtain optimum release of acyclovir from topical formulations, the outer phase of an oil-in-15 water emulsion composition, i.e. the aqueous phase, contains the maximum concentration of dissolved drug. Furthermore, it has been found that by using a high concentration of a polyhydric alcohol as an auxiliary solvent in the aqueous phase, e.g.

20 at least 50% v / v of this phase, can achieve an increased concentration of dissolved acyclovir, leading to increased efficacy and efficacy of such formulations. Such a high concentration of a polyhydric alcohol also makes it unnecessary to incorporate a preservative as additional component of the formulation.

Such topical formulations also satisfy the criteria for the necessary stability and retention of action and are not too irritating to skin 30 or mucosa, and they have the advantage over the known formulation that they penetrate the skin more effectively and in greater concentration with the result that a rapid and complete cure for the infection is achieved.

35 In order to obtain a formulation having the above advantageous properties, the ingredients of the formulation on a weight / weight basis must be within specific limits. Thus, the formulation of the invention is characterized in that it comprises 1 to 10% w / w acyclovir or a salt or ester thereof, 30 to 5 50% w / w of the polyhydric alcohol and 20 to 40% w / w water, wherein the percentages are based on the total weight of the formulation.

As mentioned above, a problem with the formulation described in Example 2 of English Patent No. 1,523,865 was the low penetration of the active ingredient into the skin. In contrast, the formulation of the present invention has been found to provide significantly better penetration or penetration of the active ingredient through the skin.

This difference in penetration through the skin is a parameter that is difficult to quantify in practice, but the experimental report below provides data demonstrating this improved penetration. In the test report, a topical 20 formulation according to Example 2 of the present application is compared to a cream prepared in accordance with Example 26 of British Patent Specification No. 1,523,865. As will be seen, the test report describes the testing of the two formulations in the treatment of a topical herpes infection in guinea pigs, and the cream of the present invention provides a much faster cure of the infection than the cream of the prior art. Since the two creams are administered with the same concentration of active ingredient in exactly the same way, the difference in healing effect of the two formulations must be attributed to a difference in the penetration of the active ingredient through the skin, ie. a pharmaceutical-technical effect.

In the following, references to acyclovir 35 should be construed to include also pharmaceutically acceptable salts and esters thereof, unless otherwise clearly stated in the context.

In a preferred embodiment, the formulation of the invention comprises 2 to 5% w / w acyclovir, 35 to 45% w / w of the polyhydric alcohol and 25 to 40% w / w water. The formulation preferably contains about 40% w / w of the polyhydric alcohol.

A polyhydric alcohol is an alcohol having two or more hydroxy groups. Among polyhydric alcohols suitable for incorporation into the topical formulation prepared by the process of the invention may be mentioned glycols and macrogols such as propylene glycol, butane-1,3-diol, polyethylene glycol and glycerol, with propylene glycol being the preferred alcohol.

When at least 50% v / v of a polyhydric alcohol in the aqueous phase of the formulation according to the invention is used, the maximum concentration of acyclovir at ambient temperature rises from 0.15% w / w which is the maximum solubility of acyclovir in water, to 0.3% w / w. Thus, when 20 concentrations of more than 0.3% w / w aqueous phase acyclovir are incorporated into a formulation, the amount of active ingredient beyond 0.3% will be in suspension and act as a reservoir for the drug. The amount of acyclovir present in the formulation must be at least sufficient to be antivirally active and non-toxic. The water used in the formulation is preferably purified water, that is, purified in accordance with the regulations of British

Pharmacopoeia.

30

The oil phase of the present formulation can be prepared from known ingredients in known manner.

While the phase may contain only one emulsifier, it preferably contains a mixture of at least one emulsifier with a fat or oil or with a fat and an oil. As further explained below, a hydrophilic emulsifier is preferably incorporated together with a lipophilic emulsifier which acts as a stabilizer. It is also preferred to incorporate both an oil and a fat. Together, the emulsifier or emulsifiers with or without stabilizer or stabilizers form the so-called emulsifying wax, and the wax together with the oil and / or the fat constitutes the so-called emulsifying ointment base which forms the disperse oil phase in the emulsions.

Topical oil-in-water compositions can be formulated in several ways, all of which depend primarily on the orientation of the emulsifier and emulsion stabilizer at the oil / water interface, with the non-polar or lipophilic groups soluble in the oil phase and the polar or hydrophilic or lipophilic groups in the aqueous or continuous phase. Thus, the more polar hydrophilic emulsifiers result in oil-in-water emulsions. This principle has been put into practice with the idea of a "hydrophilic-lipophilic balance" (H.L.B.) Griffen, W. C, J.Soc. Cos. Met. Chem., 1954, f5, page 249, and the various emulsifiers have been assigned H.L.B numbers on the basis of which it can be predicted how they will behave together with constituents of the aqueous phases and the oil phases.

It is a recognized theory in the formulation of oil-in-water emulsions that a lipophilic emulsifier can be combined with a hydrophilic emulsifier 25 of the same chemical species in varying proportions to obtain the desired H.L.B. value. With the high concentration of polyhydric alcohol required to maximize acyclovir release from the formulation of the invention, it is convenient to have a HLB value of from 3.5 to 10.0, preferably 4.0 to 8.0, and best ca.

5.5, while for comparison, the accepted H.L.B. range for mineral oil-in-water emulsions is 8 to 18.

Among the emulsifiers and emulsion stabilizers suitable for preparing the formulation of the invention are polyoxyethylene sorbitan monostearate (polysorbate 60), sorbitan monostearate, sorbitan monooleate, cetostearyl alcohol, myristyl alcohol, sodium monostearate sodium and glyceryl glyceryl A preferred combination of emulsifiers is cetostearyl alcohol and sodium lauryl sulfate in a ratio of from 3: 1 to 30: 1, preferably from 6: 1 to 20: 1, and most preferably from 9: 1 to 15: 1.

The formulation may optionally contain other emulsifiers, e.g. poloxamers, in an amount of from 0.1 to 3% w / w, preferably 0.3 to 2% w / w, and most preferably about 1% w / w, of the formulation.

The choice of suitable oils or fats for the formulation is made in order to obtain the desired cosmetic properties since the solubility. of acyclovir in most oils that may be used in pharmaceutical emulsion formulations is very low.

Thus, a cream should preferably be a non-greasy, non-stain and washable product of appropriate consistency to avoid leakage from tubes or containers. Mono or dibasic straight or branched chain alkyl esters may be used, such as e.g. diiso adipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, iso-propyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a mixed ester of 2-ethylhexanoic acid with a mixture of ethyl acetate or a mixture of cetyl ", the latter three being preferred esters. These esters can be used alone or in combination depending on the desired properties. Alternatively, high melting lipids such as e.g. white soft paraffin and / or paraffin oil or other mineral oils.

The described topical pharmaceutical formulation can be prepared by mixing the combination of acyclovir, polyhydric alcohol and water with the oil phase.

35 The manner in which the emulsion is formulated will, of course, vary according to the amount and nature of the constituents, but the formulation is nevertheless in accordance with prior art emulsion technology 7 149131 (cf. The Pharmaceutical Codex, London, The Pharmaceutical Press, 1979). For example, acyclovir may first be incorporated wholly into the aqueous portion, where it may form only a solution or a mixed solution / suspension, and then emulsified with the ointment basis. When high concentrations of acyclovir may alternatively be formulated a portion of the aqueous portion. as an emulsion, after which the residual water of polyhydric alcohol and acyclovir is added and dispersed in the emulsion. In another technique, acyclovir can be incorporated into the emulsion ointment prior to emulsification with the aqueous portion. Using these methods, it is preferred to heat the aqueous portion and the ointment base to ca. 40 to 80 ° C, preferably 50 to 15 70 ° C, before the emulsification which can be carried out by vigorous stirring using, for example, a conventional laboratory mixer. Finer dispersions of the oil phase can be obtained by homogenization or comminution in a colloid mill.

A topical formulation such as the present invention can be used to treat or prevent viral infections caused by, for example, Herpes zoster, Herpes varicella and Herpes simplex types 1 and 2, which cause such diseases as e.g. shingles, 25 chicken pox, Herpes labialis and Herpes genitalis.

The formulation should most conveniently be applied to the affected area of the skin or mucosa from 2 to 6 times daily, preferably from 3 to 4 times.

The invention is further explained by means of the following examples and experimental report.

Example 1 2% w / w aqueous cream 35 An aqueous cream was prepared from the following ingredients: 1. Acyclovir 20.0 g 2. Cetostearyl alcohol, B.P. 67.5 g 3. Sodium lauryl sulfate, B.P. 7.5 g 4. White, soft paraffin, B.P. 125.0 g 5 5. Paraffin Oil, B.P. 50.0 g 6. Propylene glycol, B.P. 400.0 g 7. Purified water, B.P. to 1000.0 g 2 g of the acyclovir used were dissolved in the water and the propylene glycol at ambient temperature to form an aqueous solution. The paraffins (4,5) and emulsifiers (2,3) were mixed with each other and heated to 60 ° C, then emulsified with the aqueous solution, also at 60 ° C, using a laboratory mixer at 8000 rpm.

The remaining amount of acyclovir was added, the mixture dispersed, allowed to cool and filled into lacquered aluminum tubes.

Example 2 5% w / w aqueous cream 20 In the manner described above, an aqueous cream containing 5% w / w acyclovir was prepared.

Example 3 0.2% w / w aqueous cream 1. Acyclovir 2.0 g 2. Isopropyl myristate, B.P. 100.0 g 3. 2-Ethylhexyl palmitate 50, Q g 4. Lys paraffin oil, B.P. 50.0 g. 5. Cetostearyl alcohol, B.P. 30.0 g 6. Glyceryl monostearate, B.P. 16.0 g 7. Polysorbate 60, B.P.C. 4, and 8. Propyl engly co 1, 'B.P. 400.0 g 9. Purified water, B.P. to 1000.0 g of 33 The cream was prepared in the manner described in Example 1, except that the entire amount of acyclovir was initially dissolved in the propylene glycol / water constituents (8,9).

9 149191

Example 4 2% w / w aqueous cream

An aqueous cream was prepared from the following ingredients by the procedure described in Example 1.

1. Acyclovir 20.0 g 2. Cetostearyl alcohol, B.P. 67.5 g 3. Sodium lauryl sulfate, B.P. 7.5 g 4. White, soft paraffin, B.P. 125.0 g 10 5. Paraffin Oil, B.P. 50.0 g 6. Butane-1,3-diol, B.P. 400.0 g 7. Purified water, B.P. to 1000.0 g

For search report 15 l. The following is an account of the test of two pharmaceutical formulations containing 9- (2-hydroxyethoxymethyl) quanine (acyclovir).

2. The two formulations are as follows: a) Topical cream with 5% acyclovir, formulation 20 of the present invention.

FORMULATION

Ingredients Quantity for 10 kg charge

Acyclovir, micronized (factored) 500.0 g

Cetostearyl alcohol BP 675.0 g

Sodium lauryl sulfate BP 75.0 g

White soft paraffin BP 1250.0 g

Paraffin Oil BP 500.0 g Propylene Glycol BP 4000.0 g

Purified water 3000.0 g

Method of Manufacture.

A. Weigh the acyclovir into a beaker.

B. The propylene glycol / water mixture is prepared in a stainless steel container and mixed with a glass rod.

149191 ίο C. The active compound is dispersed in a portion of the propylene glycol / water mixture using a high shear mixing apparatus.

D. The remaining mixture is heated to 70 ° C using a steam bath.

E. The cetostearyl alcohol, sodium lauryl sulfate, white soft paraffin and paraffin oil are fused together and heated to 70 ° C in a stainless steel vessel using a steam bath.

10 P. D is added to E and made up to the correct weight with water and emulsified using a high shear mixer.

G. It is cooled to 45 to 50 ° C.

H. The suspension of active compound from C is added, 15 and it is well mixed and cooled rapidly in an ice bath and stirred until the mixture solidifies at room temperature.

b) Topical cream with 5% acyclovir, formulation according to Example 26 of English Patent No. 1523865.

FORMULATION

Ingredients For 1 kg charge

Acyclovir, micronized (factor) 50.0 g

Anhydrous lanolin BP 200.0 g

Polysorbate 60 BP 40.0 g

Sorbitan monopalmitate 20.0 g

Light Paraffin Oil 40.0 g 3Q Propylene Glycol BP 50.0 g

Methyl hydroxybenzoate BP 1.0 g

Purified water BP 599.0 g

Method of Manufacture.

A. The acyclovir is dispersed in 100 ml of water.

B. The propylene glycol and the remaining water are mixed together, the mixture is heated to 60 ° C and the methyl hydroxybenzoate dissolved therein.

The anhydrous lanolin, polysorbate 60, the sorbitan monopalmitate and the light paraffin oil are fused at 60 ° C.

D. B is added to C and emulsified, made up to 5,850 g with water and cooled to 45 ° C and the suspension of active compound added and dispersed.

E. Cool to room temperature while mixing.

3. The testing of the above formulations was carried out as described below.

Method.

The study of the two cream formulations was performed on 12-14 week old female albino guinea pigs of a weight of 600-700 g each (obtained from Porcellus Animal Breeding Ltd., Heathfield, Sussex, England). The animals were housed individually or in pairs and received as feed F.D.I.

(Frant Diet No. 1 obtained from Oxoid Labs., H.C., Styles (Bewdley Ltd.), Bewdley, Worcs., England) and water at 20 libitum.

Both flanks of each guinea pig were shaved tightly and the remaining coat was removed with a threaded hair removal cream (Immac.). The exposed skin areas were then washed and dried. Four hours later, eight 25 sites on each flank were lightly scratched using a dull scalpel blade through a drop of a H31 strain of herpes simplex virus type 1 g containing 10 pfu / ml (pfu = plaque forming units).

Herpes simplex virus type 1 strain H31 was grown from 30 from a culture taken from the neck with a cotton swab on St.

Mary's Hospital, Paddington, London and provided by Dr. D. Jeffries as passage 2 in human embryonic lung cells. It has since been grown in VERO cells and is at passage 10, and it has been stored as a crude cell culture extract in 1 ml volume at -70 ° C.

This strain produces a self-limiting infection which is not fatal.

12 149191

Treatment with the creams began 18 hours after infection, with small papules and erythema at the site of infection becoming visible. The aforementioned cream of English Patent No. 1523865 was administered to the right flank of two guinea pigs and the above cream of the present invention was similarly administered to the right flank of ten guinea pigs, using the left flank of each guinea pig as untreated control. The treatment was continued twice daily for three days.

The size, number and spread of the pustules, the extent of erythema and the development of crustaceans and their subsequent detachment were assessed daily.

3.5

Results.

Cutaneous infection of guinea pigs with herpes simplex virus type 1 strain H31 is self-limiting, being of 12-14 days duration. After 24 hours, 20 small numbers of papules and local erythema become visible, and the papules develop after another 24 hours into pustules increasing in size and number, eventually growing together. The erythema is amplified and individual pustules develop within 4 days of infection. The wound crusts continue to develop for up to 7-8 days, at which time a large crust or row of wound crusts covers each site of infection. The wound crusts are loosened 12-14 days after infection, which emphasizes the self-limiting nature of the infection and the similarity to human skin infections.

The extent of the infections on each animal was assessed daily, starting at 24 hours after the first treatment and continuing until the end of treatment, and then at intervals until the healing process was complete. Each infection site on the flank of the animal is assigned a number value as follows: 13 149191

Number value f A) Specific erythema around the site of infection 0-1-2-3 B) Cure at site of infection 0-1-2 C) Bust formation - size, number and whether they are confluent 0-1-2-3 5 D) Wound crust formation 0- 1-2 E) Area of infection beyond the infected 0-1-2

The numerical values of the infection sites on each flank 10 were then added together.

Daily determined numerical values for treatment with the cream of the invention.

Time after initiation of treatment (days)

No. 0. 1 2 3 5

T j C TCTCTCTC

1 17 19 23 42 10 52 6 60 2 44 2 20 20 32 43 15 54 12 59 2 44 20 3 18 19 28 40 16 50 8 59 3 44 4 20 25 31 45 15 53 9 60 1 39 5 19 20 16 40 8 46 3 56 0 38 6 19 19 24 41 13 46 10 57 2 40 7 16 17 41 40 16 46 7 55 1 41 8 25 24 27 41 19 47 13 56 3 38 9 17 19 23 43 19 45 12 61 1 39 25 10 18 18 26 43 10 49 9 59 2 43 18.9 20.0 27.1 41.8 14.1 48.8 8.9 58.2 1.8 41.0 2> 5 2> 5 1 6 '7 | 3/8 I 3.3] 3tl 2.0 1.0 2.5

Daily determined numerical values after treatment with the cream 30 according to English Patent No. 1,523,865.

Time after starting treatment (days)

Animal No. J \ 2 3 6

35 TCTCTCTCTC

1 18 18 18 34 11 44 21 58 14 61 2 16 16 26 35 19 44 16 57 28 62 1 17 I 1? 22 I 34, S IS 44 IS, S 57.5 21 61.5 14 149191

The mean values were then plotted graphically against "days after commencement of treatment" to obtain the graphical representation shown in the drawing.

At the end of the cream 5 treatment according to English Patent No. 1,523,865 (3 days), the viral replication is reduced significantly compared to the control areas where the lesions have their maximum spread, but the remnants of the infection sites in the treated areas are still visible. For comparison, at the end of treatment with the cream of the invention (3 days), there is no visible evidence of infection, only a general erythema.

Three days after the end of treatment with the cream according to English Patent No. 1,523,865 (6 days) there is no active infection and the healing is progressing. Examination of the control areas shows that the healing process has begun and that the wound crust formation is beginning. In comparison, the healing is complete three days after the end of the 20 cream treatment according to the invention (6 days) and there is no visible evidence of the previous infection and no ulcer * 4. From this experiment it can be concluded that both the tested creams exhibit antiviral action against infection with herpes simplex virus type 1, but the cream of the invention provides a greater healing rate resulting from improved penetration of the skin.